Locks of this type on the one hand serve for being able to lock the door from the outside, so that no unauthorized person can enter from the outside, but also on the other hand to ensure that the door can always be opened from the inside. Such doors are applied for escape ways, emergency exits and likewise and in particular they are stipulated with regard to refrigeration rooms and freezer rooms, in order to ensure that a person accidentally shut inside can leave the room at any time.
Mortise locks which have this function are counted as belonging to the state of the art. They comprise a door handle on their inward and outward sides and these via a common square shank engage in a hub which is rotatably mounted within the lock. The hub comprises a catch, with which the latch bolt can be displaced into the opening position. A locking cylinder is integrated for the dead bolt function and this activates a dead bolt which is arranged parallel to the latch bolt, usually therebelow and which can be extended and retracted by way of turning the key in the cylinder lock. On the inward side, an operating element is fixedly connected to the cylinder lock, instead of the key, so that the door can be unlocked from the inside also without a key.
The disadvantage of this known lock, in particular if it is applied for the door of a refrigeration room or freezer room, is that two operating elements must always be actuated one after the other, in order to open the lock and thus the door. Firstly, the dead bolt is to be unbolted by way of the operating element arranged on the cylinder lock, whereupon the door handle located thereabove is to be actuated.